Radiator cooling fans not calling when AC is on



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Thread: Radiator cooling fans not calling when AC is on

  1. #1
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    Radiator cooling fans not calling when AC is on

    Hello, I just recently picked up a 2000 Limited T&C 3.8L with 105K.
    The issue I am trying to work through is the two under hood electric fans will not come on when the AC is turned on.
    I have replaced the fan relay, that I found under the driver headlight. I have checked the 40 amp fuse and its good. I have run just the engine up to temp and the fans will run based on coolant temperature. Dash coolant gauge works normally. I have jumpered the two wires at the relay connection and fans run. I have cleaned the two body ground tabs under the battery tray, that was told grounds the PCM.? The ac compressor clutch engages when the ac button is on.
    Not sure where to go from here? If I have a bad PCM would other items be effected?
    thanks

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  3. #2
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    1 out of 1 members found this post helpful.
    Your PCM is fine. Your A/C pressure transducer switch may not be. It tells the PCM to turn the fans on when the pressures are up to spec. Could be wiring between. Don't recall where it is.
    ******** We took the time to answer your post. Please give us some time and post the fix. You'll help hundreds. ********

    **** Follow all prescribed safety procedures before attempting any repairs. If in doubt, refer to a maintenance manual. ****

    96 Gr Caravan LE 3.8, 214K miles
    07 Fusion / 06 RAV 4 / 06 Accord

  4. #3
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    It IS possible to get a brand new relay that's bad.
    If nothing else works I would try one from a junk yard to test the fans if you don't want to buy another new one.

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  6. #4
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    RIP. thanks. I found the 3 wire pressure transducer on the small high side line near the firewall, just left of the alternator pulley. Is there also one on the low side line? I did not find one.
    I will put some gauges on the system and see if the pressures look good. If low then add some to bring pressure up and the transducer will start reading? Hopefully this will get it and the fans will operate with ac switch on.
    will post more as I get info. thanks

  7. #5
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    RIP. thanks again.
    You were correct about the pressure transducer being the item. I found that the ac system was low on 134a and added some. during the add process, the two electric cooling fans came on.
    they are now running and the ac is cycling / cooling much better.

  8. The Following User Says Thank You to trkpny For This Useful Post:

    RIP(05-20-2017)

  9. #6
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    Great news. Wish they were all that easy.

    BTW - The fact your fans were coming on as the engine temp rose tells you the fan relay and PCM are doing their job. The PCM uses data from the pressure switch and the engine cooling temp sensor to determine when the fans come on. If either say GO, the PCM sends a signal out a single wire to the fan relay. The relay then applies power to the fan motors.
    Last edited by RIP; 05-20-2017 at 05:29 PM.
    ******** We took the time to answer your post. Please give us some time and post the fix. You'll help hundreds. ********

    **** Follow all prescribed safety procedures before attempting any repairs. If in doubt, refer to a maintenance manual. ****

    96 Gr Caravan LE 3.8, 214K miles
    07 Fusion / 06 RAV 4 / 06 Accord

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